1992 Saturn sl1 slowly loosing fuel economy

[JasonG]

They are also very sensitive to Intake Air Temp.

Hope that fuel filter fixed it.

[jakobnev]

So any chance your car is fine and it's just the outdoor temps getting you down?

Large seasonal variations are quite common, especially for those who drive shorter trips.

[Highjumphero]

Originally Posted by jakobnev

So any chance your car is fine and it's just the outdoor temps getting you down?

Large seasonal variations are quite common, especially for those who drive shorter trips.

Originally Posted by Highjumphero

It is also not seasonal/climate thing, as I have had the car for 3 years taking the same route.

Worst I have ever got on a tank in the past was 32, that was before I adjusted the nut behind the steering wheel.

[Highjumphero]

I think the fuel filter could be the culprit! I don't have any solid evidence yet, but my mileage seems to be improving. Also I installed a Mpguino in the spring and it never seemed to work right, mainly the actual mileage and the readout were never close after many calibrations, and also the "current mileage" did not change (sometimes got better) under engine load like going up a hill, or driving at higher speeds. Well today I noticed it was responding to engine load.

Again only the pump will tell if my mileage is improving, but I have wondered how a clogged fuel filter could reduce your mileage, It seems counter intuitive.

This is my hypothesis. I am mechanically minded, but I am not an auto mechanic so bear with me here! First I had to realize fuel injectors do not forcefully inject fuel into the engine, they are a plunger valve that opens and releases fuel pressurized by the pump. In turn low fuel pressure from the clogged filter caused a bad spray pattern from my injector. The poorly atomized fuel did not burn as completely, and the O2 sensor detects unburned oxygen. This then prompts for more poorly atomized fuel on the next cycle.

What do you think, am I missing anything here?

[Milwaukee]

Had you change thermostat? Couple of my fleet need new thermostat every couple years of winter.


On my exp with fuel filter in my F350 diesel 7.3L. I notice little loose power and fuel mileage was 13 That when I bought. Replace fuel filter it was cover in brown goofy and STUNK too. Now it average 15 and seem running quieter or it just my image.


With that picture of fuel filter you show. I am worry about fuel pump most time they go bad when you replaced old fuel pump. For me I prefer replace them every 30K-50K miles if I drive highway alot.

On Diesel I do at 10K-15K on fuel filter.

[JRMichler]

Try a compression test. Low compression can be caused by a leaky valve or bad rings or bad head gasket. Any of those will ruin your gas mileage. A cylinder leakdown test is even better because it will tell you exactly what is causing a loss of compression.